The invention relates to production system control methods, and specifically to a method for efficiently routing and scheduling operations in a production system on elements of a work product.
An Appendix is attached hereto and is a part of the disclosure hereof.
In general, production systems create a variety of work products in response to external orders or demands by allocating and applying multiple resources to perform work on components, or "pieces," of the work products, assembling the pieces, and discharging the completed products from the system. Each resource is typically a single worker performing a single task on one or more pieces at a time. The task and the worker/task combination is referred to herein as a "station." A job is produced by passing its constituent pieces through a sequence of stations. The sequence of stations through which each piece passes is referred to as the "route" for the piece.
As a piece is presented to a station for the task to be performed on it, the station's operator must generally consult a control document, containing information from the job order such as a drawing or set of instructions, to ensure that the operator performs the appropriate task on the piece. At a station, a piece may be created, merged with other pieces into a smaller number of pieces, or eliminated.
A particular work product to be made in response to a particular work order, referred to herein as a "job," will typically have an associated deadline specified in the work order. Each of the constituent pieces of the job have a "priority" for handling by the system that is determined by the deadline or by other criteria. Such a system usually has many jobs in progress at once, so that several pieces may concurrently require operation by the same resource. The order in which a resource operates on a piece is determined by the priority of the piece or the job with which it is associated.
The most efficient use of a production system occurs when work products are discharged from the system in such a way as to maximize the number of work orders that are satisfied with products of adequate quality within the deadline specified for each order with the minimum expenditure of resources. Conventional control methods for such systems do not yield the most efficient use of the system. Conventional systems involve significant manual effort in determining how to route pieces through the system and how to prioritize work done on the pieces by each station and in presenting the appropriate control document to the station as the corresponding piece reaches the station for operation. The systems are relatively inflexible in that it is difficult to change the routes that pieces take through the system without disrupting the system's operation.